1. Field of the Invention
The invention resides in the field of pulmonary artery balloon catheters and more particularly relates to low inflation pressure, low deflated profile, self centering polyurethane devices.
2. Description of the Prior Art
Pulmonary artery balloon catheters for measuring pressures within the vascular system are well known devices in the medical field. Their primary purpose is, after insertion into the body of the patient, to provide a means for performing such measurements by inflating the balloon attached to the catheter tip. This is accomplished, for example, by the introduction of fluid into the balloon through the catheter by a syringe located externally to the patient. These catheters are intended to be left within the body for an extended period of time and therefore their construction as well as their maneuverability, manipulation, and activation with minimum danger to the patient are of great concern.
The primary material for manufacturing these balloons heretofore has been latex. There are a number of drawbacks to the use of latex which are alleviated entirely or in part by the employment of polyurethane in accordance with applicants invention. Among these drawbacks are the following.
Inflation of latex balloons is erratic due to the high tension of the material compared to polyurethane. This results in a surge to full size when the critical inflation pressure is reached as well as a tendency to inflate non uniformly or out of round nearest the catheter inflation port.
As a natural material, latex varies from lot to lot, decomposes or spoils easily and is difficult to extrude with even wall thickness.
Mechanically, it is not as durable as polyurethane, fragments when it bursts, diffuses filling gases quickly and absorbs bodily fluids. Further latex has a rougher surface making balloons composed of that material more difficult to introduce into the body and more likely to promote blood clots upon long periods of in-dwell.
Additionally latex has undesirable toxins and pollutants from its source and processing and can cause severe allergic reactions in some patients.
Finally it is not as easily mounted on a catheter requiring adhesives and metal bands which may be avoided with polyurethane by using solvents.
The use of polyurethane as a catheter balloon material has however been disclosed in the prior art. For example U.S. Pat. No. 4,913,701 Tower, describes a polyethylene catheter employing a thermoset polyurethane balloon attached by cuffs and an appropriate adhesive. The references contained therein particularly U.S. Pat. No. 4,661,095, Taller et al. further disclose various aspects of the technology involved in this endeavor.
Applicant has now discovered that by constructing such catheters and balloons of a particular material in a particular way, a superior device can be created which overcomes many of the deficiencies of those comprised of latex and those comprised of polyurethane as has been previously disclosed.